Stretch-straightening machine with actuating means intermediate the gripping heads



Sept. 16, 1958 H LORANT 2,852,062

STRETCH-STRAIGHTENING MACHINE WITH ACTUATING MEANS INTERMEDIATE THE GRIPPING HEADS Filed March 8, 1956 2 Sheets-Sheet l l' l n a I (I) I ,9

l' I I u I I SOURCE OF PRESSURE INVENTOR HUGO LORANT.

-----,-- av ERIC MICHELSON AGENT.

Sept. 16, 1958 H. LORANT 2,852,062

STRETCH-STRAIGHTENING MACHINE WITH ACTUATING MEANS INTERMEDIATE THE GRIPPING HEADS Filed March 8, 1956 2 Sheets-Sheet 2 INVENTOR HUGO LORANT.

ERIC MICHELSON AGENT United Etates Patent 2,852,062 Patented Sept. 16, 1958 fiiice STRETCH-STRAIGHTENING MACHINE WITH AC- TUATING MEANS INTERMEDIATE THE GRIP- PING HEADS Hugo Lorant, New York, N. Y.

Application March 8, 1956, Serial No. 570,277

Claims. (Cl. 153-35) This invention relates to stretch-straightening machines for ferrous and non-ferrous material such as plates, sheets, bars, rods, profiles and the like. Machines of this type are used to stretch material beyond the yield point so that waves or bends as encountered, for example, in rolled or extruded parts will be eliminated permanently. At the same time the strength characteristics of metal treated will generally be improved as a result of cold working.

Stretch-straightening machines normally comprise two gripping heads which engage the material to be handled. In conventional machines, one of the heads is locked to a frame in adjustable position while the other head is movable on the frame and connected to actuating means. During the stretching operation the relatively long frame is under compression and in most cases is subject to a large eccentric load, which makes it necessary to provide heavy and expensive structures. Further, the locking means for the adjustable gripping head are costly and subject to substantial wear since they transmit the full stretching force, and their operation is time-consuming as they reequire careful alignment before locking. It has been proposed to arrange longitudinal frame members symmetrically to the stretching axis, which will avoid eccentric forces, but such frame members still participate in the transmission of the load, and locking means are required to secure the adjustable head to the frame members.

Furthermore, it is necessary to provide for the absorption of shocks as they occur if the material to be straightened breaks during the stretching operation. Shock absorbing means used in the past have increased the cost of the machine and have not worked entirely satisfactorily.

It is an object of the invention to avoid the above dis advantages and provide an improved stretch-straightening machine which is relatively simple and inexpensive.

It is also an object of the invention to eliminate the transmission of operating stresses through frame members in machines of the above type and at the same time to arrange the actuating means so that unilateral eccentric stresses are avoided in the force-transmitting members.

Another object is to reduce buckling stresses in force- 'transmitting members by providing an arrangement in which such members are relatively short.

It is a further object of the invention to facilitate adjustment of the gripping heads along the bed, which will result in increased production.

A still further object is to provide a machine of the above type in which shocks are absorbed in a highly efiicient and safe manner by using inherent parts of the assembly for this purpose.

These and other objects and advantageous features of the invention will be apparent from the following detailed description and the drawings which are merely exemplary.

In the drawings which are partly diagrammatic,

Fig. 1 is a plan view, partly in section, of a stretchstraightening machine embodying the invention;

Fig. 2 is a sectional view taken along line 2-2 of Fig. 1;

Fig. 3 is an end view of the machine;

Fig. 4 is an enlarged sectional view of a detail.

Referring to the drawings, the machine illustrated therein has relatively wide gripping means adapted for the leveling of metal sheets or plates but it will be clear that the invention may likewise be applied to stretchers for straightening other elongated material such as bars, rods, etc.

The machine is provided with a bed having guideways 12 on which two gripping heads 14, 16 are slideable. Each of the heads has gripping jaws 18 of the conventional type, which are movable by means such as fluidoperated cylinders 20 and links 22, to engage or disengage material to be stretched.

Fluid-operated means such as a pair of cylinder-pistonassemblies generally indicated at 24, 26 are supported on the bed and engaged by keys as shown at 28 in Fig. 2. It should be noted that the keys 28 do not transmit stretching forces to the bed but merely serve to position the cylinder-piston-assemblies relative to the bed. Each of the assemblies 24, 26 comprises a cylinder 30 having hydraulic chambers 32, 33 which communicate with each other through a central chamber 36, and pneumatic chambers 38, 39. A pair of double-acting pistons 42, 43 are arranged to operate in opposite directions and have front faces 46, 47 (Fig. 4) subject to hydraulic pressure and rear faces 48, 49 subject to pneumatic pressure. A closure member 52 is arranged at each end of cylinder 30 and held in place by means of a split ring 54. Each of the closure members 52 carries a gland 56 and packing 58.

The central chambers 36 of both assemblies 24, 26 are connected through pipes 60 to a control valve 62 which is selectively adjustable for connection to a source of hydraulic pressure and to an exhaust line and also has a neutral position for locking fluid in chambers 32, 33, 36. The source of hydraulic pressure may be an accumulator connected to a pump, or a direct pump drive may be provided, and the hydraulic fluid may be either water or oil. Pipes 64 serve for constant communication'between chambers 38, 39 and a source of pneumatic pressure such as a tank diagrammatically indicated at 65 and filled with compressed air, the pneumatic pressure being generally lower than the hydraulic pressure;

Each of the pistons 42, 43 is provided with a piston rod 66 having external threads 68. Mounted on bed 10 at the ends thereof are supports 70, 71 which have openings 74 (Fig. 3) in which the piston rods 66 are guided for longitudinal movement, the rods being secured against rotation by means of keys '76. Each of the gripping heads 14, 16 is provided with two rotatable bushings 78, 79 which are threaded internally along a part of their length, and which receive the piston rods 66 and are in mesh with the threads 68. Each bushing has a shoulder 82 and a nut 84 on its circumference to secure the bushing against axial movement relative to its gripping head. A

An electric motor 86 is positioned on each gripping head and carries a sprocket wheel 88 which is connected through a chain 90 to a sprocket wheel 92 rigidly mounted on each bushing 78 by means of a tapered key or the like. To accommodate the wheels 92, the bushings 78 are somewhat longer than bushings 79. A further sprocket wheel 93 is rigidly mounted on each bushing 78 between the associated gripping head and wheel 92 and engages a chain 94 which passes over a sprocket wheel 96 rigidly mounted on each bushing 79 so that both bushings 78, 79 will be turned together upon actuation of the respective motor 86.

At the start of the operation, the position of the gripping heads 14, 16 is adjusted along the bed in accordance object is defective.

the length of the workpiece such as a plate 98 indicated in dotted lines in Figs. 1 and 2. For this purpose, one or preferably both motors 86 are energized so that bushings 7 8, 79 will be rotated and the gripping heads will be caused to travel along piston rods" 66. This motion may be continued until the ends of plates 98 are positioned within the jaws 18 whereupon the jaws w ll be closed by means of cylinders 20 to grip the material. The adjustment of the heads is thus carried out in a fast and expedient manner as it is not necessary to disengage any gripping head from the bed and lock it afterwards-to the bed'again and as both heads may travel simultaneously.

Control valve 62 .is then adjusted to admit hydraulic fluid under pressure through pipes 60 and central chamber 36 to chambers 32, 33 so as to cause pistons 42, 43 and their piston rods 66 to move outwardly in opposite directions. As the threads 68 of the piston rods are in mesh with and bear against the internal threads of bushings 78, 79 of the gripping heads 14, 16, the motion of the piston rods will be imparted to the gripping heads which will in turn act through jaws 18 upon the plate 98 so as to stretch the plate along axis X-X. It will be clear that the operating forces are thus transmitted by the actuating members directly to the gripping head assemblies, and that bed is entirely free of such forces and merely serves to support the dead weight of the parts. No auxiliary framework is required to take up the operating forces. The members subject to compression, that is, the piston rods 66, are relatively short as compared with the total length of the machine since they extend from the intermediate assemblies 24, 26 to either gripping head; therefore, buckling stresses are relatively low. As the axes of the assemblies 24, 26 are arranged symmetrically at opposite sides of the stretching axis X-X, unilateral eccentric forces are avoided. In the embodiment shown, the jaws and the axes of the assemblies 24, 26 and of the rods 66 are disposed in a horizontal plane through the stretching axis X-X so as to eliminate substantially all bending moments in the bed 10, assemblies 24, 26 and rods 66. The assemblies 24, 26 are spaced transversely of the stretching axis X-X so as to accommodate the workpiece 98 between the assemblies.

While the pistons 42, 43 perform the working stroke, they overcome the constant pneumatic pressure in chambers 38, 39 as the areas of the front faces 46, 47 of the pistons are larger than the difierential areas at 48, 49 and, moreover, the hydraulic pressure is generally higher than the pneumatic pressure. Compressed air will thus be returned from chambers 38, 39 through pipes 64 to tank 65 during the working stroke.

After plate 98 has been stretched a predetermined degree to straighten the plate, control valve 62 is brought to its neutral position to lock fluid in chambers 32, 33, 36, and the jaws 18 are opened. The gripping heads 14, 16 are then moved further apart a short distance by admitting hydraulic pressure again to cylinders 30, or by energizing the motors 86, to withdraw the jaws from plate 98 which thereupon is removed from the machine. Control valve 62 is adjusted to connect chambers 32, 33 to exhaust, which will enable the constant air pressure in chambers 38, 39 to return pistons 42, 43 to their initial positions. The machine is now ready for the next operating cycle.

During stretching, the plate or other workpiece is sometimes torn apart, for example, in case the material of the If this happens, the gripping heads and associated parts will he suddenly realeased from restraint and tend to move apart abruptly under the pressure exerted by the actuating means. Accordingly, as stated hereinbefore, it is necessary to provide protective means. In the machine illustrated, the fluid-operated means 24, 26 are positioned substantially at the midpoint between the gripping heads 14 and 16, and the masses movable in opposite directions are approximately equal. In case of breakage of the material to be stretched, the energies released in opposite directions will be substantially balanced, which will greatly facilitate the absorption of shocks. Moreover, any tendency of the gripping heads and associated structures to move outwardly upon breakage of the workpiece will be counteracted efficiently by the compressed air in chambers 38, 39 which are under constant pressure. Thus, the return means serve at the same time as shock absorbing means, which will not only reduce the cost of the machine but also increase the safety as these return means are an inherent part of the actuating mechanism. The movable parts of the machine will not transmit any substantial shock to the bed and foundation since the balanced energies of these parts will be sustained within the assemblies 24, 26.

While a preferred embodiment of the invention has been described, it will be understood that various modifications and changes may be made without departing from the scope and spirit of the invention as defined in the appended claims. For example, instead of using cylinders having hydraulic and pneumatic chambers within the same bore to actuate differential pistons, each cylinder-piston-assembly may comprise a hydraulic cylinder with a separate coaxial pneumatic cylinder arranged adjacent each end thereof. It will be clear that in this case each piston rod may have two separate pistons mounted thereon, one of which will operate in the hydraulic cylinder of the respective assembly while the other piston will operate in one of the pneumatic cylinders.

Having described my invention, what I claim and desire to secure by Letters Patent is:

l. A stretch-straightening machine comprising a bed, a pair of gripping heads movable on said bed relative to each other along a predetermined stretching axis, gripping jaws in said heads for engaging material to be stretched, a pair of cylinder-pistomassemblies arranged intermediate the gripping heads at opposite sides of the stretching axis, said assemblies being spaced from each other so as to accommodate said material therebetween, a pair of threaded piston rods extending from each of said assemblies in opposite directions towards the gripping heads, internally threaded means on said heads in mesh with and rotatable relative to the piston rods, and actuating means for rotating said threaded means and rods relative to each other to adjust the position of said heads longitudinally of the rods, said rods being operable by said assemblies to move the heads away from each other and stretch said material.

2. A stretch-straightening machine as specified in claim 1, in which the piston rods are secured-against rotation and said internally threaded means are in the form of bushings rotatably mounted in the gripping heads but secured against axial displacement relative to said heads, and in which motor means are operatively connected to the bushings for turning said bushings to adjust the position of said heads.

3. A stretch-straightening machine comprising a bed,

a pair of gripping heads movable on said bed relative to each other along a predetermined stretching axis, gripping jaws in said heads for engaging material to be stretched, one pair of coaxial rods atone side of and parallel to said stretching axis and a symmetrically arranged pair of rods at the other side of said axis, each of said rods being connected to one of said gripping heads and extending therefrom towards the midpoint between said heads, said stretching axis, jaws and the axes of said rods being disposed substantially in a common plane, and fluid-operated means disposed coaxially with and intermediate each pair of rods approximately at the midpoint between said heads and connected to a common source of fluid pressure to simultaneously move the rods of each pair and their respective gripping heads in opposite directions to stretch said material with substantially all bending moments being eliminated in the bed,

rods and fluid-operated means, the masses movable in opposite directions being approximately equal whereby in case of breakage of said material the energies released in opposite directions are substantially balanced.

4. A stretch-straightening machine as specified in claim 3 in which each of said fluid-operated means has means connected thereto to pull back said rods and their gripping heads after a stretching operation and to absorb said energies released in case of breakage of said material.

5. A stretch-straightening machine as specified in claim 4, wherein each of said last-named means is pneumatically operated.

References Cited in the file of this patent UNITED STATES PATENTS Thielmann June 19, 1906 Hatch et al. May 31, 1932 Borwick Nov. 15, 1938 Oeckl Jan. 13, 1942 Flowers Apr. 11, 1944 Sharpe Sept. 27, 1949 Bath July 19, 1955 

